$::foo refers to the global variable called foo in the main package, not in the current package.

This works out the same for package main, but it just doesn't DWIM for other packages. The first three times I read through the documentation, I assumed it was just refering to this similarity: clearly, the writers of the Perl parser could tell what package they were in, so they could expand $::foo appropriately. After all, they need to figure out packages for function calls. Instead, it means the same as $main::foo, something that a simple regexp could do for me, if I wanted it to.

Since I thought the point of the package notation was to let the globals stand out with the double colon sigil syntax, I was disappointed to learn that I'd have to hard-code the package name in multiple places: first, in the the package, and second, for all the global variables within that package.

"our" variables solve the hard-coded package name issue, but don't have a special sigil to make them stand out as globals anymore...*sigh*
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Ytrew

In Perl 6, :: behaves more like you expect, and is no longer automatically associated with either package main or any other top-level package. Class names are searched for starting in the current package, so
$::foo would be a variable in the current package if declared there.